A graph search is attractive for quantitative analysis of volumetric medical images, especially for layered tissues, because a graph search allows globally optimal solutions in low-order polynomial time. However, because the volume data can be represented as nodes in an orthogonal graph in Euclidean space, segmentation may not achieve greater precision than a single unit, or distance between two adjoining nodes, and partial volume effects may be ignored. These and other shortcomings are addressed by the present disclosure.